The university was investigating to find out who was involved.

CBS San Francisco reports.

University Of Oregon Students Who Trashed Shasta Lake Apologize

EUGENE, Ore. (CBS/AP) — University of Oregon sororities and fraternities are planning service projects at a California campsite where about 1,000 people left trash that took dozens of National Forest workers six hours to clear.

The Register-Guard reports the Interfraternity Council and the Panhellenic Council said in an apology statement that many university fraternities and sororities were among those camping along Lake Shasta at Slaughterhouse Island the weekend of May 20.

The Greek letters Lambda Chi Alpha were printed on an abandoned cooler.

A university official said the U.S. Forest Service will direct a clean-up by the chapter that will likely include items left behind after an expected visit by University of California at Davis students.